In the steel industry there is a need to stabilize i.e. reduce unwanted motions and vibrations of moving metal strips or sheets. The stabilization is especially important in hot-dip galvanizing lines.
In hot-dip galvanizing lines, the metal strip to be galvanized is moved through a bath of molten zinc. When the metal strip leaves the zinc bath, an air-knife blows off the excess zinc to reduce the thickness of the coating to the desired value. By reducing the vibration of the metal strip, the air-knife action (wiping) can be better controlled and the coating thickness made more uniform. This allows the coating to be made thinner and this saves zinc, reducing the weight of the product and reduces costs.
Vibrations in the galvanizing line originate from imperfections in the line's mechanical components. Vibrations can be accentuated at high line speeds and on longer unsupported or free strip paths. Additional movements and vibrations of the strip originate from air flowing on the strip, both from the air-knifes and cooling air.
WO2006101446A1 (Loefgren et. al.) entitled “A device and a method for stabilizing a steel sheet” present a device for stabilizing an elongated steel sheet which is continuously transported in a transport direction along a predetermined transport path. The device comprises at least a first pair, a second pair and a third pair of electromagnets with at least one electromagnet on each side of the steel sheet, which are adapted to stabilize the steel sheet.
U.S. Pat. No. 6,471,153B1 (TETSUYUKI et. al.) entitled “Vibration control apparatus for steel processing line” relates to an apparatus for controlling vibration of steel sheet being processed in a processing line. The apparatus includes: electromagnet devices for generating magnetic forces acting at right angles on the steel sheet; sensor devices for detecting separation distances between the steel sheet and the electromagnet devices. In U.S. Pat. No. 6,471,153B1 each electromagnet devices is controlled by one measurement by one sensor device. No information from other sensor devices is used to correct or adapt the generated magnetic force from a device.